What is the common cause of a parse error in PHP code and how can it be resolved?

A common cause of a parse error in PHP code is missing or mismatched parentheses, brackets, or quotes. To resolve this issue, carefully check the syntax of your code and ensure that all opening characters have corresponding closing characters. Additionally, using a code editor with syntax highlighting can help identify these errors more easily.

// Incorrect code with missing parentheses causing a parse error
echo "Hello, world";
```

```php
// Corrected code with added parentheses
echo "Hello, world";